Answer:
20 metres
Explanation:
Given that the area of a triangle is 30 square metres (m²). Using the equation A = 1/2bh, this is the formula for the triangle.
where b is base and h is height
Given that b = 3 metres.
To calculate h, Substitute b and A into the equation
30 = 1/2 × 3 × h
3h = 60
h = 60/3
h = 20 m
Therefore, h is equal to 20 metres
Answer:
a. 0.21 rad/s2
b. 2.205 N
Explanation:
We convert from rpm to rad/s knowing that each revolution has 2π radians and each minute is 60 seconds
200 rpm = 200 * 2π / 60 = 21 rad/s
180 rpm = 180 * 2π / 60 = 18.85 rad/s
r = d/2 = 30cm / 2 = 15 cm = 0.15 m
a)So if the angular speed decreases steadily (at a constant rate) from 21 rad/s to 18.85 rad/s within 10s then the angular acceleration is
b) Assume the grind stone is a solid disk, its moment of inertia is
Where m = 28 kg is the disk mass and R = 0.15 m is the radius of the disk.
So the friction torque is
The friction force is
Since the friction coefficient is 0.2, we can calculate the normal force that is used to press the knife against the stone
This one is a piece 'o cake if you know the formula for
Kinetic Energy, and impossible if you don't.
It is: KE = (1/2) (mass) (speed²) .
For this object: KE = (1/2) (30 kg) (20 m/s)²
= (1/2) (30 kg) (400 m²/s²)
= (15 x 400) (kg-m²/s²)
= 6,000 joules .
In that case, there are three possible scenarios:
-- If the braking force is less than the force delivered by the engine,
then the car will continue to accelerate, and the brakes will eventually
overheat and erupt in flame.
-- If the braking force is exactly equal to the force delivered by the engine,
then the car will continue moving at a constant speed, and the brakes will
eventually overheat and erupt in flame.
-- If the braking force is greater than the force delivered by the engine,
then the car will slow down and eventually stop. If it stops soon enough,
then the absorption of kinetic energy by the brakes will end before the
brakes overheat and erupt in flame. Even if the engine is still delivering
force, the brakes can be kept locked in order to keep the car stopped ...
They do not absorb and dissipate any energy when the car is motionless.